Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual era a superfície quando o oponente era Sergiy Stakhovsky Mikhail Youzhny?
 ###Tabelas: CREATE TABLE summary_of_results (summary_of_results_id AUTO_INCREMENT PRIMARY KEY, Party VARCHAR, Burnley INT, Chorley INT, Fylde INT, Hyndburn INT, Lancaster INT, Pendle INT, Preston INT, Ribble Valley INT, Rossendale INT, South Ribble INT, West Lancashire INT, Wyre INT, Total INT) CREATE TABLE tournament_for_the_championship_of_canada (tournament_for_the_championship_of_canada_id AUTO_INCREMENT PRIMARY KEY, Players VARCHAR, Games Won INT, Games Lost INT, Total points INT, Grand Average VARCHAR, Best Winning Average VARCHAR, Best Run INT) CREATE TABLE regular_schedule (regular_schedule_id AUTO_INCREMENT PRIMARY KEY, Game VARCHAR, Day, Date VARCHAR, Anand VARCHAR, Gelfand VARCHAR, Standing VARCHAR) CREATE TABLE u.s._nielsen_weekly_ratings (u.s._nielsen_weekly_ratings_id AUTO_INCREMENT PRIMARY KEY, Episode VARCHAR, Rating INT, Share INT, 18–49 (Rating/Share) VARCHAR, Viewers (m) INT) CREATE TABLE doubles:_6_2–4 (doubles:_6_2–4_id AUTO_INCREMENT PRIMARY KEY, Outcome VARCHAR, Date VARCHAR, Surface VARCHAR, Partner VARCHAR, Opponents VARCHAR, Score VARCHAR)  
SELECT Surface FROM doubles:_6_2–4 WHERE Opponents = sergiy stakhovsky mikhail youzhny